package offerv1;

import leetcodev1.链表.Solution;

public class Offer25 {
    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
        ListNode virtual = new ListNode(-1), index = virtual;
        while (l1 != null || l2 != null) {
            int num1 = l1 != null ? l1.val : Integer.MAX_VALUE;
            int num2 = l2 != null ? l2.val : Integer.MAX_VALUE;

            if (num1 < num2) {
                index.next = l1;
                l1 = l1.next;
            } else {
                index.next = l2;
                l2 = l2.next;
            }
            index = index.next;
        }

        return virtual.next;
    }

    public ListNode mergeTwoLists1(ListNode l1, ListNode l2) {
        ListNode prehead = new ListNode(-1);

        ListNode prev = prehead;
        while (l1 != null && l2 != null) {
            if (l1.val <= l2.val) {
                prev.next = l1;
                l1 = l1.next;
            } else {
                prev.next = l2;
                l2 = l2.next;
            }
            prev = prev.next;
        }

        // 合并后 l1 和 l2 最多只有一个还未被合并完，我们直接将链表末尾指向未合并完的链表即可
        prev.next = l1 == null ? l2 : l1;

        return prehead.next;
    }
}
